[Bug c/34109] New: Incorrect code for tail calls with a structure as 4th argument

[Bug c/34109] New: Incorrect code for tail calls with a structure as 4th argument

[narge-gcc at derrin dot id dot au]

In the following code, the tail call in g() is compiled incorrectly on ARM with
-O2 or higher (and -fno-inline):

#include <stdio.h>

struct s {
    int x, y, z;
};

int f(int a, int b, int c, struct s d, int e) {
    printf("%d %d %d\n", d.x, d.y, d.z);
    return 0;
}

int g(int a, int b, int c, int d, struct s e, int h) {
        return f(a, b, c, e, h);
}

int main(void) {
    f(0, 0, 0, (struct s){ 42, 69, 105 }, 7);
    g(0, 0, 0, 0, (struct s){ 42, 69, 105 }, 7);
    return 0;
}

With -O1 and lower, the result is correct:

42 69 105
42 69 105

With -O2 and higher, it prints:

42 69 105
69 69 7

Inspecting the output of gcc -O3 -fno-inline -S shows that gcc is shifting the
arguments on the stack downwards for the tail call. However, it starts at the
top, rather than at the bottom. So it writes over two arguments (e.z and e.x)
before loading them.

This has been broken since 4.1.1 (possibly earlier), and is still broken in
4.2.2.


-- 
           Summary: Incorrect code for tail calls with a structure as 4th
                    argument
           Product: gcc
           Version: 4.2.2
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: narge-gcc at derrin dot id dot au
GCC target triplet: arm-elf


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=34109

[Bug middle-end/34109] Incorrect code for tail calls with a structure as 4th argument

[pinskia at gcc dot gnu dot org]

------- Comment #1 from pinskia at gcc dot gnu dot org  2007-11-15 18:53 -------
I think this is already fixed in 4.3.0.


-- 

pinskia at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
          Component|c                           |middle-end
           Keywords|                            |wrong-code


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=34109

[Bug middle-end/34109] Incorrect code for tail calls with a structure as 4th argument

[rguenth at gcc dot gnu dot org]

-- 

rguenth at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |WAITING


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=34109

[Bug middle-end/34109] Incorrect code for tail calls with a structure as 4th argument

[ramana dot r at gmail dot com]

------- Comment #2 from ramana dot r at gmail dot com  2009-03-17 14:40 -------
This appears to be fixed on mainline on gcc version 4.4.0 20090317
(experimental) (GCC). 

output obtained
42 69 105
42 69 105


-- 

ramana dot r at gmail dot com changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |rearnsha at gcc dot gnu dot
                   |                            |org, ramana dot r at gmail
                   |                            |dot com


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=34109

[Bug middle-end/34109] Incorrect code for tail calls with a structure as 4th argument

[rearnsha at gcc dot gnu dot org]

------- Comment #3 from rearnsha at gcc dot gnu dot org  2009-03-18 11:49 -------
No feedback in over a year.  Presumed fixed in 4.3.0.


-- 

rearnsha at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|WAITING                     |RESOLVED
         Resolution|                            |FIXED
   Target Milestone|---                         |4.3.0


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=34109

[Bug middle-end/34109] Incorrect code for tail calls with a structure as 4th argument

[mikpe at it dot uu dot se]

------- Comment #4 from mikpe at it dot uu dot se  2009-03-20 11:08 -------
(In reply to comment #3)
> No feedback in over a year.  Presumed fixed in 4.3.0.

I can confirm that this test case works when compiled with a vanilla gcc-4.3.3
built for armv5tel eabi.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=34109